1. Field of the Invention
The present invention pertains to electrolytic filter press cells. More particularly, the present invention pertains to chlor-alkali electrolytic filter press cells. Even more particularly, the present invention pertains to protective coverings for chlor-alkali electrolytic filter press cell frames.
2. Prior Art
The advent of electrolytic filter press cells for the manufacture of chlorine and caustic has given rise to a wealth of technology with respect thereto. Because of the strong oxidation conditions present in the cell, much research has been expended to derive and define inexpensive materials of construction which will not degrade within the cell environment. Moreover, the prior art has sought materials which will enhance the useful life of the structures disposed within the cell. Thus, there has been taught heretofore the coating of electrodes with fluorohydrocarbons to protect the base material of the electrode. See, inter alia, U.S. Pat. Nos. 3,645,796; 3,461,044 and 3,679,568.
It is to be further appreciated with respect to the prior art that in most instances prolongation of the useful life has been directed to the electrodes, the diaphragm, if present, and the cell structure, including electrical connections. In connection herewith, it is to be noted that very little attention has been paid to the cell frame or barrier which separates adjacent electrodes. Generally, most cell frames are molded or otherwise manufactured from filled or unfilled synthetic resinous materials. Conventionally, most cell frames comprise polypropylene which may be filled with materials such as, asbestos or calcium silicate. Other types of synthetic resins used for cell frames include graphite-filled phenol-formaldehyde resins, as taught in U.S. Pat. No. 3,415,733. However, and as noted, filled or unfilled polypropylene is the prevalent material of construction for electrolytic filter press cell frames. This is especially true in a chlor-alkali environment.
However, it has been found that polypropylene cell frames are subject to chemical attack by the electrolytes. This chemical attack can result in a shortened life for the cell frame. More detrimental, however, is that the anolyte solution attacks the cell frame and forms particulate matter therewithin. This particulate matter has been found to plug or foul the cell diaphragm or membrane. This not only damages the diaphragm or membrane but, also, reduces cell efficiency. The present invention, as will subsequently be detailed, alleviates this problem. Concurrently, the present invention enables the use of materials for cell frame construction which are normally incompatible with the electrolyte solutions.